China's space agency launched two astronauts, or taikonauts, Monday morning into low Earth orbit aboard its Shenzhou 11 spacecraft. If all goes according to plan, in two days they will dock with China’s Tiangong 2 space station, where the taikonauts will stay for 30 days to test its habitability and to carry out medical and scientific experiments.

Monday’s launch marked the sixth time China has sent taikonauts into space, and the beginning of the country’s longest crewed mission yet as it builds towards missions deeper into space.

"You are going to travel in space to pursue the space dream of the Chinese nation," said Fan Changlong, a vice chairman of China's Central Military Commission, as China’s state news agency Xinhua reported.

The Shenzhou capsule was launched aboard a 191-foot-tall Long March-2F rocket from the Jiuquan Satellite Launch Center on the edge of northern China's Gobi Desert. Inside of it were taikonauts Jing Haipeng and Chen Dong, according to Wu Ping, deputy director of China's manned space engineering office, who spoke from a televised news conference.

Mr. Jing has flown to space on two other missions, in 2008 and 2012. "It is any astronaut's dream and pursuit to be able to perform many space missions," Jing said at a separate briefing. He will turn 50 in space, reported the government-run China Youth Daily newspaper.

The Tiangong, or "Heavenly Palace," is China’s version of the International Space Station, a multinational program that China is barred from participating in, mostly because of the US government’s security concerns.

China was barred from the ISS in 2011, when the US Congress passed a law prohibiting official American contact with the Chinese space agency due to concerns about national security, reports Time.com.

The 2011 law draws a sort of ex post facto justification from a study that was released in 2012 by the US-China Economic and Security Review Commission, warning that China’s policymakers “view space power as one aspect of a broad international competition in comprehensive national strength and science and technology.”

More darkly, there is the 2015 report prepared by the University of California, San Diego’s Institute on Global Conflict and Cooperation, ominously titled “China Dream, Space Dream“, which concludes: “China’s efforts to use its space program to transform itself into a military, economic, and technological power may come at the expense of US leadership and has serious implications for US interests.”

The Tiangong 2 is expected to be completed and begin operating fully in 2022. It will run for at least a decade, providing a bridge towards a Chinese mission to Mars by the end of that decade.

Tiangong 2’s predecessor, Tiangong 1, launched in 2011 and went out of service in March. Before shutting down, it had docked three visiting spacecraft and extended its mission for two years.

China’s first crewed space mission came in 2003, when it became the third country after Russia and the US to launch humans to space. By 2008, Chinese taikonauts conducted a spacewalk, and in 2013 it became the third country to land a rover, Yutu, on the moon. It’s possible that China will land taikonauts on the moon in the future.